The present invention relates to a system for arranging circuits and components for monitoring gases, humidity, smoke, temperature, pressure, vibrations, rpms, speed, and other environmental factors. The system also provides for controlling alarms to alert system operators to potential dangers.
Environmental monitors protect life and property. In an industrial setting, such detectors typically use remote sensors so that the presence of smoke, hazardous gases, excessive humidity, temperature variations, or the like may quickly be detected at a remote location of a facility or process. Other monitors provide information regarding ambient pressure, humidity and/or temperature, or vibration, speed, and/or RPMs of nearby machinery or vehicles. These monitors may also be adapted to measure optical obscuration, turbidity, radio frequency, viscosity, force and weight, torque and electrical and mechanical parameters such as voltage, current, frequency, shock, vibration and acoustics. This information is usually reported electronically to a control room. Relevant parameters (e.g., concentration of a noxious gas, average RPMs, etc.) are recorded and analyzed by computer and alarms, or other signal means (hereinafter alarms) are automatically activated when the measured parameter exceeds or falls below certain preset values or ranges.
Conventional prior art sensors are individually wired to the field location from a central control panel, using whatever number of wires are required to deliver the power and return the information. There are usually a minimum of three to five wires for each sensor. Boxes located in the field interconnect the wiring from the field location to a central computer read-out. As the number of sensors increases, the number of wires to be brought into the read-out area also increases, making the read-out area increasingly complex, and making installation of the sensors and read-out difficult and costly.
Supporting electronics for monitoring large numbers of monitors in close proximity usually occupies a vast amount of wall space and require expensive conduit, cables, and labor to interconnect.
Major problems in any detection and alarm system are safety and reliability. To ensure safety and efficacy, an operator must frequently check and calibrate each sensor in the alarm system. Such periodic calibration is necessary to ensure the accuracy of the sensors. Furthermore, sensors for hazardous gases which are lighter than air (e.g., methane, hydrogen) are often situated high above the ground, making it inconvenient, even dangerous, to physically approach the sensor to apply calibration gas and adjust the output.
Leach et al., in U.S. Pat. No. 4,555,930, provide a system for minimizing the number of wires used to connect sensors to a control room. Each sensor has its own digital code, so that, when the satellite unit addresses a sensor, the sensor responds with a code that differs from the satellite unit by one parity bit. This system provides zero and span calibration of the sensors. The odd/even parity transmission mode makes it possible to connect a plurality of sensors to a satellite subassembly.
Redding, U.S. Pat. No. 4,119,950, discloses an apparatus for monitoring gas content on a site comprising a transmitter for feeding ultrasonic waves through the gas to a receiver. A plurality of transmitter/receiver pairs can be enabled in sequence to monitor a large area, with the respective frequencies or phase displacement monitored by a central processor. However, there is no indication that the connections to the central processor can be minimized in any way.
Gulbrantson, U.S. Pat. No. 4,067,004, discloses a remote carbon monoxide monitoring system, including a control panel and remote alarm stations. Although the system can be connected to a large number of remote alarm stations, there is no indication that connections to the control panel can be minimized by any type of arrangement.
Klein et al., U.S. Pat. No. 3,090,038, disclose a hazardous atmosphere detecting and signaling system for combustible gases which is less than that which will produce an explosion in the air at that moment. In this apparatus, the gas sampled is enriched with the gas to be detected and exploded.
Other gas sensing devices are shown in U.S. Patents to Ogg, U.S. Pat. No. 3,482,233; Chavis, U.S. Pat. Nos. 4,340,885; 4,119,950; Hayden, U.S. Pat. No. 3,789,231; Stetter et al., U.S. Pat. No. 4,384,925; Murphy, U.S. Pat. No. 5,576,739; Tanigawa, U.S. Pat. No. 3,978,476; and Dunham et al., U.S. Pat. No. 3,209,343.
It is an object of the present invention to overcome the aforesaid deficiencies in the prior art.
It is another object of the present invention to provide a unique arrangement of circuits and components to facilitate field installation of monitoring sensors.
It is a further object of the present invention to provide a system for environmental monitoring in which sensors can be calibrated from a safe, remote location.
It is a further object of the present invention to provide a system for environmental monitoring having an integrated field panel for connections from the sensor clusters to a central monitoring location.
According to the present invention, a complete and modular arrangement of wiring for remote sensors and monitoring stations is provided which comprises a communication box for managing large numbers of sensors throughout large buildings, mines, tunnels and other such facilities. The system of the present invention comprises long distance communications, remote calibration and regulator modules, and optional intrinsic safety barriers in one compact module. Also included are relays for controlling alarms and plant functions. The module can optionally house an AC/DC power supply with attendant backup batteries. A strobe and horn can be added, as well as essential field switches, for emergency stop and alarm reset.
In the system according to the present invention, remote sensors are positioned so as to provide the most effective, accurate measurement of one or more parameters of interest. For example, in measuring the concentration of a gas, such as propane, which is heavier than air, sensors are located near the ground or the floor. Conversely, for a gas, such as methane, which is lighter than air, sensors are located high above ground level. For measuring temperature, the sensors are located where temperature variations are most critical. One skilled in the art can readily determine the optimum location for sensors for other conditions, without undue experimentation. The system also provides intrinsic safety barriers for measuring any hazardous conditions such as the presence of explosive mixtures.